Control of relative humidity (RH) is desirable in a variety of areas.
Within an electronic instrument it is desirable to control internal RH since the moisture within an instrument may affect performance and reliability. One such example is a disc drive. Control of the moisture or relative humidity within the housing that encloses the disc drive is important since moisture may affect the performance and reliability of the head/disc interface such as head-to-disc disc stiction. High moisture may increase media corrosion. Excessive disc wear has been observed under conditions of low relative humidity. Thus humidity control over an extended period of time within a moisture range is desirable.
Desiccants are used to control relative humidity in a number of situations. One category of desiccants includes polymeric desiccants. Polymeric desiccants are widely used to absorb water in liquid form in diapers and sanitary napkins. Such polymeric desiccants can absorb water many times their own weight and typically are referred to as superabsorbents since their purpose is to absorb as much water as possible. Such prior art superabsorbents are useful for a single cycle absorption of water.
In protecting the electronic instruments from humidity, a desirable desiccant should be able to withstand many absorption-desorbption cycles while still maintaining humidity control over the life of the instrument. Carbon-silica gel desiccants are presently used to maintain humidity control in electronic instruments.